Forces occur due to interactions between two or more objects. When one object exerts a force on another, the second object simultaneously exerts an equal and opposite force on the first. This is described by Newton's Third Law of Motion, which states that forces always come in pairs, often called action and reaction forces

. These interactions can be of two main types:

• Contact forces , where the objects physically touch each other. Examples include friction, normal force, tension, applied force, and spring force. For instance, friction arises because the microscopic roughness of surfaces causes them to resist sliding past each other

• Non-contact forces , where objects exert forces without touching, such as gravitational and electromagnetic forces. Gravity causes masses to attract each other even across distances

In essence, force occurs whenever there is an interaction between objects, either by direct contact or through a field, and it manifests as a push or pull that can change the motion of objects

Summary:

• Forces are interactions that occur in pairs (action and reaction).
• They can be contact forces (requiring physical touch) or non-contact forces (acting at a distance).
• Forces cause changes in motion by overcoming inertia or balancing other forces like friction